The present invention relates to a method for the preparation of 2-halogenoresorcinols having the following formula I ##STR2## where X represents a halogen atom and R and R.sub.1 may be the same or different and represent a hydrogen atom or a free organic functional or functionally modified group or a hydrocarbon group, which may be substituted by one or more free organic functional or functionally modified groups and R and R.sub.1 jointly may also represent a free organic functional or functionally modified group or a hydrocarbon group which may be substituted by one or more free organic functional or functionally modified groups, and esters, ethers, or salts thereof.
The method of the invention comprises sulfonating the corresponding resorcinols which do not contain a halogen in the 2-position and then halogenating the sulfonic acids thus obtained. The halogenated sulfonic acids thereby obtained are subsequently protodesulfonated by acid hydrolysis and, if desired, any functional groups which may be present can be modified.
The halogenoresorcinols of formula (I) are compounds which in recent years have become industrially important. For example, in U.S. Pat. No. 4,296,039 it is disclosed that 2-chlororesorcinol and 2-bromoresorcinol can be used to prepare coumarins which are halogenated in the 8-position and which may be used for medicinal purposes. The known methods for preparing 2-halogenoresorcinols do not give satisfactory results. In particular, direct halogenation of the resorcinols produces halogen-derivative mixtures which are difficult to separate; and the transformation of the resorcinols in dihydroresorcinol, followed by halogenation and the elimination of hydrohalogenacids with the formation of halogenoresorcinols, has proved to be difficult to perform on an industrial scale.